Cleansing compositions that are mild to the hair and skin and are perceived to provide the sensory attributes that consumers associate with healthy, moisturized hair and skin have become increasingly popular in recent years.
Although various mild surfactant systems have been proposed as the basis of such cleansing compositions there is generally a trade-off between the mildness of a composition and its ability to produce a rich abundant lather. Consequently when using mild surfactants, formulators often increase the total surfactant content to overcome this lather deficiency. Not only does this adversely affect the economics of the composition but this can also reduce the mildness of the composition since the ability of a surfactant to interact with the proteins present in hair and skin depends on the total surfactant concentration in addition to other factors. Furthermore, high concentrations of surfactants can also interfere with the efficient delivery of insoluble hair and skin conditioning agents that are desirable to incorporate in moisturizing shampoo compositions.
Thus there remains a need for surfactant compositions that are mild to hair and skin and yet are efficient in terms of producing a rich, abundant lather without the need to use excessive levels of surfactant in the composition and which are highly compatible with insoluble hair conditioning agents.
While studying a variety of mild cleansing compositions, it has been found that binary mixtures of certain sulfosuccinate surfactants and amphoteric surfactants used alone or in further combination with alkyl ethoxy sulfates and other surfactants can provide highly efficient and mild shampoo and skin cleansing bases. However, these bases had highly variable and unpredictable storage stability. Some combinations became very viscous, even gelling during storage and were unacceptable to consumers while others having what appeared to be the same “nominal” composition did not.
Extensive study and chemical analysis indicated that it was the interaction of hydrolysis products of the sulfosuccinate surfactant with the amphoteric surfactant that was responsible for the anomalous thickening in storage. Furthermore it was surprisingly found that the level of sulfosuccinic acid or its simple salt that was present in the composition had a pronounced and critical effect on storage stability, especially under high temperature storage conditions. These findings provided the basis for making practical shampoo and skin cleansing compositions that employ a sulfosuccinate surfactant in combination with an amphoteric surfactant. These combinations have the advantage of providing very mild compositions that do not compromise lather, are efficient and economical and are highly compatible with hair and skin conditioning agents.
These and other advantages of the compositions disclosed herein will become clear from the description of the invention.
The following patents and publications have been considered:
WO93/25650 discloses highly concentrated (30-90%) surfactant concentrates that include an alkyl polyglycoside and an effective amount of a viscosity-adjusting agent selected from the group consisting of inorganic and organic electrolytes. Carboxylic acids and their salts are mentioned as organic electrolytes.
U.S. Pat. No. 4,668,422 describes compositions based on alkylpolyglycosides and amphoteric surfactants with optional small amounts of anionic surfactant. Sodium chloride and ammonium chloride are disclosed as viscosifying agents, i.e., materials that increase the viscosity of the composition.
U.S. Pat. No. 4,839,098 discloses a liquid dishwashing detergent consisting essentially of alkyl glucoside and dialkylsulfosuccinate. Ammonium chloride is disclosed as a viscosity regulator.
U.S. Pat. No. 6,165,454 discloses a low energy method for making hair care products including an anionic surfactant, a water insoluble silicone and an acrylic stabilizing agent.
U.S. Pat. No. 6,306,805 discloses surfactant compositions that include a cationic surfactant, an anionic surfactant and a bridging surfactant.
The present invention seeks improvements over deficiencies in the known art. Among the one or more problems addressed include storage instability.